Gene Mutation Flashcards
What is a mutation?
Any change to the quantity or the base sequence of the DNA or an organism
What effect can inherited mutations have on individuals?
They often produce sudden and distinct difference between individuals
When can mutations be inherited?
When they occur during the formation of gametes
Define a gene mutation
A change to one more nucleotide bases, or a change in the sequence of the bases, in DNA
How can a gene mutation affect a polypeptide?
By changing the sequence of triplets, leading to a change in the sequence of amino acids in the polypeptide
When do gene mutations typically arise?
Spontaneously during DNA replication
Name two types of gene mutation
Base substitution and Base deletion
How can a single amino acid change affect a protein?
If the original amino acid was important for bonds that determine the tertiary structure, the replacement may change the protein’s shape and function
What is a base substitution?
It is a type of gene mutation where a nucleotide in a DNA molecule is replaced by another nucleotide with a different base
What happens if a substitution changes the active site of an enzyme?
The active site may no longer fit the substrate, and the enzyme will no longer catalyse the reaction
Why might a base substitution have no effect on the protein?
This is because of the degenerate nature of the genetic code - different triplets can code for the same amino acid
What is a base deletion mutation?
A gene mutation where a nucleotide is lost from the normal DNA sequence
Why can deletion of just one nucleotide have a large effect?
This is because it can cause a shift in the reading frame, changing the way all subsequent triplets are read
How does base deletion usually affect the polypeptide?
It usually produces an entirely different amino acid sequence, making the polypeptide unlikely to function correctly
Why does a single base deletion change the reading frame?
DNA is read in triplets, so deleting one base shifts all triplets to the left by one base
How can chromosome mutations arise?
They can arise spotaneously
What are chromosome mutations?
Changes in the structure or number of whole chromosomes
What is polyploidy?
A condition where organisms have three or more sets of chromosomes instead of the usual two, mostly occurring in plants
What causes a change in the number of individual chromosomes?
Non - disjunction, where homologous chromosomes fail to separate during meiosis
What happens to offspring when non - disjunction occurs?
They have more or fewer chromosomes than normal in all their body cells
